Re: [PATCH V4] Fix NULL dereference in super_by_fd

[Coly Li <colyli@suse.de>]

On Wed, Dec 21, 2022 at 05:37:52PM +0800, Li Xiao Keng wrote:
> When we create 100 partitions (major is 259 not 254) in a raid device,
> mdadm may coredump:
> 
> Core was generated by `/usr/sbin/mdadm --detail --export /dev/md1p7'.
> Program terminated with signal SIGSEGV, Segmentation fault.
> #0  __strlen_avx2_rtm () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:74
> 74		VPCMPEQ	(%rdi), %ymm0, %ymm1
> (gdb) bt
> #0  __strlen_avx2_rtm () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:74
> #1  0x00007fbb9a7e4139 in __strcpy_chk (dest=dest@entry=0x55d55d6a13ac "", src=0x0, destlen=destlen@entry=32) at strcpy_chk.c:28
> #2  0x000055d55ba1766d in strcpy (__src=<optimized out>, __dest=0x55d55d6a13ac "") at /usr/include/bits/string_fortified.h:79
> #3  super_by_fd (fd=fd@entry=3, subarrayp=subarrayp@entry=0x7fff44dfcc48) at util.c:1289
> #4  0x000055d55ba273a6 in Detail (dev=0x7fff44dfef0b "/dev/md1p7", c=0x7fff44dfe440) at Detail.c:101
> #5  0x000055d55ba0de61 in misc_list (c=<optimized out>, ss=<optimized out>, dump_directory=<optimized out>, ident=<optimized out>, devlist=<optimized out>) at mdadm.c:1959
> #6  main (argc=<optimized out>, argv=<optimized out>) at mdadm.c:1629
> 
> The direct cause is fd2devnm returning NULL, so add a check.
> 

The patch is fine to me. But the following changelog should be moved to the
location after '---'.



> V1->V2: When fd2devnm return NULL, super_by_fd return NULL but not an
> incomplete 'st' entry. At the same time, add a check in map_by_devnm
> to avoid coredump.
> 
> V2->V3: Fix style issues.
> V3->V4: Change strcpy() to strncpy().
> 
> Signed-off-by: Li Xiao Keng <lixiaokeng@huawei.com>
> Signed-off-by: Wu Guang Hao <wuguanghao3@huawei.com>
> ---

The changelog should be moved here, then they won't show up in commit
log when Jes takes this patch into mdadm git tree.

V1->V2: When fd2devnm return NULL, super_by_fd return NULL but not an
incomplete 'st' entry. At the same time, add a check in map_by_devnm
to avoid coredump.
 
V2->V3: Fix style issues.
V3->V4: Change strcpy() to strncpy().


Thanks.

>  mapfile.c | 4 ++++
>  util.c    | 7 ++++++-
>  2 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/mapfile.c b/mapfile.c
> index 8d7acb3..f72fe0d 100644
> --- a/mapfile.c
> +++ b/mapfile.c
> @@ -292,6 +292,10 @@ struct map_ent *map_by_uuid(struct map_ent **map, int uuid[4])
>  struct map_ent *map_by_devnm(struct map_ent **map, char *devnm)
>  {
>  	struct map_ent *mp;
> +
> +	if (!devnm)
> +		return NULL;
> +
>  	if (!*map)
>  		map_read(map);
> 
> diff --git a/util.c b/util.c
> index 64dd409..3a84ee3 100644
> --- a/util.c
> +++ b/util.c
> @@ -1241,6 +1241,11 @@ struct supertype *super_by_fd(int fd, char **subarrayp)
>  	int i;
>  	char *subarray = NULL;
>  	char container[32] = "";
> +	char *devnm = NULL;
> +
> +	devnm = fd2devnm(fd);
> +	if (!devnm)
> +		return NULL;
> 
>  	sra = sysfs_read(fd, NULL, GET_VERSION);
> 
> @@ -1286,7 +1291,7 @@ struct supertype *super_by_fd(int fd, char **subarrayp)
>  		if (subarrayp)
>  			*subarrayp = subarray;
>  		strcpy(st->container_devnm, container);
> -		strcpy(st->devnm, fd2devnm(fd));
> +		strncpy(st->devnm, devnm, MD_NAME_MAX - 1);
>  	} else
>  		free(subarray);
> 
> -- 
> 1.8.3.1

-- 
Coly Li